1. Field of the Invention
The present invention relates to an apparatus for driving a display panel such as a plasma display panel (PDP) or the like.
2. Description of Related Art
In a display apparatus of a matrix display system such as a PDP or the like, it is general to use two field memories as memories for display and the following operations are repeated to perform a halftone display by using a subfield method. That is, while display is performed based on pixel data of one field read out from one of the two memories, pixel data of the next one field is written into the other memory. After completion of the reading of the pixel data from one of the memories, the pixel data is read out from the other memory and is displayed and, simultaneously, the next pixel data is written into the one memory. That is, the display is performed by switching the memory on the reading side and the memory on the writing side every field.
As disclosed in Japanese Patent Kokoku No. 7-48834, a channel guiding function for automatically changing channels and displaying images of a plurality of broadcasting stations onto one picture plane, thereby facilitating the channel selection is adopted in a TV receiver or the like.
In a plasma display apparatus of a matrix display system, various pulses necessary for light emission display are generated by using a sync signal of a video signal as a reference and an image is displayed. In the case of displaying a plurality of images into one picture plane by sequentially switching a plurality of channels in a short time for a station selection of the channel guiding function or the like, when a generation timing of the sync signal is variable every channel, it is necessary to match the generation timings of various pulses for image display to the sync signal of the video signal within a short time. When the generation timings of the various pulses are deviated from the sync signal even slightly, a problem such that the picture quality of the image that is displayed on the picture plane deteriorate occurs.
In a display apparatus of a matrix display system such as a PDP or the like, in the case of displaying an image on the basis of a video signal generated by an interlaced scanning such as NTSC system, HDTV system or the like, in order to compensate a low light emission luminance, by also allocating pixel data corresponding to the odd rows (even rows) of the picture plane as they are to the even rows (odd rows), the data is interpolated, or by converting the pixel data to the pixel data of the progressive scan by a scanning line interpolating process, a display is performed by the progressive scan.
The former method, however, has a problem that a resolution in the vertical direction is not preferable. The latter method has a problem such that a memory, an arithmetic operating circuit, and the like have to be used and costs become high as a whole.
It is necessary to switch the memory on the reading side and the memory on the writing side every field in order to display a motion image. It is, however, necessary to stop the switching in order to display a still image. In order to simultaneously display both of a motion image and a still image on a picture plane, in addition to the memories, another memory for processing multi-picture planes and its control circuit are necessary, so that there is a problem such that the price becomes high as a whole.
It is an object of the invention to provide a driving apparatus of a display panel in which a disturbance does not occur in a display image on a picture plane even at the time of selecting a channel in order to solve the problems.
It is another object of the invention to provide a driving apparatus of a display panel which can reduce costs by making a scanning line interpolation processing apparatus constructed by a memory, an arithmetic operating circuit, and the like unnecessary and which can improve a resolution in the vertical direction in order to solve the problems.
It is further another object of the invention to provide a cheap driving apparatus of a display panel which can solve the problems and can simultaneously display a motion image and a still image while suppressing an increase in memory capacity.
According to a first aspect of the invention, there is provided a driving apparatus of a display panel, comprising: a television signal receiving circuit for receiving a television broadcasting wave, generating a video signal, and enabling a receiving station to be changed in accordance with an instruction; a sync signal separating circuit for detecting a sync signal from the video signal; an A/D converter for obtaining corresponding pixel data every pixel by sampling the video signal; first and second memories each having a capacity to store at least pixel data of one field; self-advancing clock signal generating means for generating a self-advancing clock signal; control means for controlling the first and second memories so as to alternately write the pixel data of one field into the first and second memories and alternately read the written pixel data of one field from the first and second memories; and display driving means for driving the display panel on the basis of the pixel data which is read out from the first and second memories, wherein the control means switches the writing and reading operations of each of the memories synchronously with the self-advancing clock signal each time that is twice or more as long as a generating period of the self-advancing clock signal and writes the pixel data of one field into the memory in response to the sync signal which is detected just after the memory was switched from the reading to the writing, and the control means reads out the pixel data written synchronously with the self-advancing clock signal and supplies it to the display driving means.
According to a second aspect of the invention, there is provided a driving apparatus of a display panel, comprising: an A/D converter for obtaining corresponding pixel data every pixel by sampling a video signal generated by an interlaced scanning; first and second frame memories for storing the pixel data; memory control means for alternately writing the pixel data into each of the frame memories and, when the pixel data of one frame is written into one of the frame memories, for reading out the written pixel data of one frame from the other frame memory; and display driving means for driving the display panel by a progressive scan on the basis of the pixel data which is read out from the first and second frame memories, wherein the memory control means stores an odd row field constructed by the pixel data corresponding to odd number designated scanning lines of the display panel into a corresponding address in the frame memory, stores an even row field which is supplied to the frame memory subsequently to the odd row field and is constructed by pixel data corresponding to even number designated scanning lines in the display panel to a remaining corresponding address in the frame memory, reads out the stored pixel data as pixel data of the progressive scan, and supplies it to the display driving means.
According to a third aspect of the invention, there is provided a driving apparatus of a display panel, comprising: an A/D converter for obtaining corresponding pixel data every pixel by sampling a video signal; first and second memories for storing the pixel data; memory control means for controlling writing and reading operations of the first and second memories so as to alternately write the pixel data into the first and second memories and alternately read out the written pixel data from the first and second memories; and display driving means for driving the display panel on the basis of the pixel data which is read out from the first and second memories, wherein each of the first and second memories has a plurality of storage areas which are allocated every plurality of pixels which are displayed in one picture plane, and the memory control means rewrites the pixel data in a predetermined storage area among the plurality of storage areas in the first and second memories.